Directions

Melt chocolate in water in microwave or in a heavy 1-qt saucepan over very low heat, stirring until chocolate melts and mixture is smooth. Remove from heat.

Position racks to divide oven in thirds. Heat to 350°F. Lightly grease bottoms of three 9-in.-round cake pans. Line with parchment or waxed paper and grease again. Coat lightly with flour, tapping out any excess.

Beat egg whites and salt in a large bowl with mixer on high speed. Gradually add the 1/2 cup sugar, beating until stiff peaks form when beaters are lifted. (Whites will be very thick, white and glossy.) Scrape whites into another bowl.

Beat butter and the 1 1/4 cups sugar in same bowl (no need to wash bowl or beaters first) until pale and creamy. Add yolks, 1 at a time, beating well after each. Beat in chocolate mixture, vanilla and baking soda.

With mixer on low speed, beat in flour in 3 additions, alternating with buttermilk in 2 additions. Stir in about 1/4 the beaten whites, then gently fold in remaining whites until just blended. Divide among cake pans; spread evenly.

Bake 2 pans on one rack, 1 on the other, 35 minutes or until cakes come away from pan sides and spring back when lightly touched in centers. Remove pans to a wire rack and run a knife between cakes and sides of pans. Let cool 5 minutes; run knife around cakes again. Invert onto rack, remove waxed paper and let cakes cool completely.

Place 1 layer on serving plate. Spread 1 cup frosting to 1/2 in. from edge. Top with second layer and 1 more cup frosting. Cover with third layer. Spread 1 cup frosting thinly over top and sides (to set the crumbs). If desired, cover cake and remaining frosting and refrigerate up to 2 days.

Up to 1 day before serving: Whip remaining frosting and swirl over top and sides of cake.

Place chopped chocolate on a sheet of waxed paper on kitchen counter next to cake. Pick up chocolate with a small metal spatula and press lightly against frosting around side of cake, or sift drink-mix powder over cake. Cover with a large bowl or use a cake keeper; refrigerate until ready to serve.

Pour 1/2 cup cream into saucepan, resting bulb of candy thermometer in liquid. Add sugar and butter and stir over low heat until sugar dissolves and mixture boils. Continue boiling, without stirring, until candy thermometer registers 238°F, or a small amount dropped into cold water forms a soft ball. Immediately remove from heat and place bottom of pan in bowl with water. Let cool to lukewarm (about 110°F).

Beat remaining 2 1/2 cups cream and the vanilla in a large bowl with mixer on medium speed until soft peaks form when beaters are lifted. Whisk or stir about 1/2 cup into the caramel, then another 1/2 cup. Add caramel mixture to remaining whipped cream and beat a few seconds until stiff. Use immediately, or cover and refrigerate up to 2 days. Rewhip briefly before using. Makes about 5 cups.